System for adding fluid fuel to furnace blast



Sept. 13, 1966 A. A. FENNELL SYSTEM FOR ADDING FLUID FUEL TO FURNACEBLAST Filed Nov. 24. 1961 5 Sheets-Sheet l INVENTOR yQJVerZ/Zefl Sept.13, 1966 A. A. FENNELL 3,272,317

SYSTEM FOR ADDING FLUID FUEL TO FURNACE BLAST Filed Nov. 24, 1961 5Sheets-Sheet 2 .157 )JW/v. J m k. m) 1 5 176 I v J5? w .155 170 1% J94J55 J40 J56 fi0 gg I J56 v 3 J74 Z0? J55 ENTOR.

p 1966 A. A.,FENNELL SYSTEM FOR ADDING FLUID FUEL TO FURNACE BLAST FiledNOV. 24, 1961 5 Sheets-Sheet 5 w w m6 My 5 M 4 a w /w w/% wmww nw w./.M* 0 w l /%w /2 d; a 3 w 7 w, "N 3 United States Patent 3,272,617SYSTEM FOR ADDIN G FLUID FUEL T0 FURNACE BLAST Anthony A. Fennel],Fennell Corp, 379 E. 147th St., Harvey, Ill. Filed Nov. 24, 1961, Ser.No. 154,551 7 Claims. (Cl. 75-42) This invention relates generally tothe operation of a blast furnace and especially to a system for addingfluid fuel to the furnace blast.

One traditional method of making steel involves use of a blast furnaceinto which there is charged a burden consisting of iron ore, coke andlimestone, the coke providing carbon for deoxidizing the iron ore aswell as fuel for heating the burden. Modern practice calls for adecrease in the customary proportion of coke in the burden and theintroduction of a fluid fuel into the air blast which is supplied to thefurnace. While this practice achieves a greater tonnage output of steelper hour of operation in addition to generally improved furnacebehavior, heretofore the rate of introducing the fluid fuel has beenestablished arbitrarily and regulated manually. As a result, the furnaceoperation has been somewhat erratic and certain safety hazards havearisen.

Accordingly, an important object of the present invention is to providea system for introducing fluid fuel into a blast furnace at a rate whichis a constant proportion of the weight of oxidizing gas beingsimultaneously introduced.

Another object of the invention is to provide such a system in which theproportion of fuel to oxidizing gas can be selectively varied.

A more general object of the invention is to provide a new and improvedsystem for automatically adding fluid fuel to a furnace blast.

Still another object of the invention is to provide a system forautomatically adding fluid fuel to a furnace blast, which system ischaracterized by uniform flow of fuel through the several tuyeres.

And another object of the invention is to provide a system for safelyand automatically adding fluid fuel to a furnace blast.

A more specific object of the invention is to provide a control systemwhich prevents fluid fuel from backing up into the blast bustle uponclogging of a tuyere and which prevents the fuel from being introducedinto the atmosphere surrounding the furnace upon the burning off of atuyere.

Additional objects and features of the invention pertain to theparticular structure and arrangements whereby the above objects areattained.

A system in accord with the invention includes means for sensing thephysical conditions of a flow of oxidizing gas to a blast furnace andfor supplying an output signal related to a selected percentage of theweight rate of flow of the oxidizing gas; means for regulating the flowof a fluid fuel to the tuyeres of the blast furnace; and means receivingthe output signal and operating the regulating means in accordancetherewith.

The invention, both to its arrangement and mode of operation, will bebetter understood by reference to the following disclosure and drawingsforming a part thereof, wherein:

FIG. 1 is a perspective view of a blast furnace incorporating a controlsystem constructed in accordance with the present invention and adaptedfor adding natural or manufactured gas to the furnace blast;

FIG. 2 is a schematic view of the blast furnace and control system ofFIG. 1, illustrating in particular the components employed inproportioning the fluid fuel being introduced into the furnace blast;

FIG. 3 is a schematic view of the components of the control system whichare particularly arranged to insure safe introduction of the fluid fuel;

FIG. 4 is an enlarged, central, cross-sectional view of one of thepressure switches used in the system of the invention;

FIG. 5 is an enlarged, central, cross-sectional view of a differentialpressure transmitting device of the type used in the system of theinvention; and

FIG. 6 is a schematic view of a modified form of the control system ofthe invention, particularly arranged for adding fuel oil to the furnaceblast.

Referring now in detail to the drawings, specifically to FIGS. 1 and 2,a blast furnace installation indicated generally by the numeral 10 willbe seen to include a blast furnace 12 comprising a tapered body 14resting on a bosh or base 16 and having an open throat 18 at its upperend. In accordance with conventional practice, the blast furnace 12 isconstructed of refractory brickwork and is intended for continuousoperation, raw materials being periodically charged into the furnacethrough throat 18 and the steel produced in the furnace beingperiodically withdrawn from the bosh 16 to be cast into pigs.

Oxidizing gases, comprising air which is sometimes enriched with oxygenand which is occasionally replaced entirely with oxygen, are required inthe operation of the blast furnace 12 in order that suflicient heat maybe developed in the reaction mass of the furnace burden to deoxidize theiron ore to steel. In compliance with conventional operations, theseoxidizing gases are directed from a supply line 20 to a header or bustlepipe 22 surrounding the blast furnace 12 in the vicinity of the juncturebetween the body and the bosh. In further compliance with customarypractice, nozzles or tuyeres 24 are employed to direct the oxidizinggases from the bustle pipe 22 into the body of the blast furnace atvarious peripheral locations. Whereas two tuyeres are shown in thedrawings, it is to be recognized that any number of tuyeres may beemployed, large furnaces frequently utilizing as many as sixteen oreighteen tuyeres.

In accordance with the present invention, supplemental fluid fuel isintroduced into the furnace, specifically into the oxidizing gases beingdirected through the tuyeres 24. The means for introducing this fluidfuel into the tuyeres are shown in FIG. 1 to include a supply line 26, aheader 28 encompassing the furnace 12 and communicating with the supplyline 26, and nozzles 30 which conduct the fluid fuel from the header 28to the individual tuyeres 24.

Since it is intended to introduce fluid fuel into the current or blastof oxidizing gas being directed into the furnace 12 in such a mannerthat the rate of addition of the fuel is a constant proportion of theweight of oxidizing gas being simultaneously introduced, the system ofthe present invention is particularly arranged to measure the flow ofoxidizing gas through the supply line 20. In addition, the system of theinvention is arranged to measure both the temperature and pressure ofoxidizing gas in order to correct the volumetric flow of oxidizing gasfor variations in either the temperature or pressure of the supply, thusin effect determining the weight rate of flow of the oxidizing gas.

Specific means for making these measurements and performing thecorrections are shown in FIG. 2. There, a primary metering deviceindicated generally by the numeral 32 will be seen connected in thesupply line 20 upstream of the bustle pipe 22. The metering device 32 isintended to measure the gross volumetric flow of oxidizing gas throughthe supply line 20 and, therefore, advantageously takes the form of anorifice meter, a nozzle meter, a venturi meter or some other suitablearrangement, desirably including valving, such as the valves 34, forpurposes of regulation.

The two output signals from the primary metering device 32, whichdifferential signals are indicative of the volumetric flow of oxidizinggas, are directed to a differential pressure transmitter 36 ofconventional construction, transmitter 36 being particularly arranged toconvert the received information to a pneumatic signal whose magnitudeis indicative of the volumetric flow through the supply line 20. Whiletrannsmitter 36 is provided with instrument air from a line 38 and aregulator 40 and while transmitter 36 is particularly arranged todevelop a pneumatic signal, the transmitter 36 ma be equally welladapted to provide either a hydraulic or an electric signal indicativeof the flow of oxidizing gas.

Continuing with reference to FIG. 2, a pressure sensor or tap 42 isconnected in supply line 20 adjacent the metering device 32; and theoutput of pressure sensor 42 is directed to a transducer 44 whichreceives instrument air from a line 46 through a regulator 48 and whichconverts the output signal of the pressure sensor to a pneumatic signalpassing through conduit 50. Similarly, a temperature sensor or well 52is connected in the supply line 20; and the output of the temperaturesensor is directed to a transducer 54 which receives instrument air froma line 56 through a regulator 58 and which converts the output signal ofthe temperature sensor to a pneumatic signal passing through the conduit60.

A pneumatic relay 62 receives the output signals from transducers 44 and54 in order to convert these signals to a single output signal to beused in correcting the measured volumetric flow of oxidizing gas forvariations in pressure and temperature. Relay 62 receives instrument airfrom a line 64 through a regulator 66; and the pneumatic output of therelay is passed through a conduit 68 to a pneumatic relay 70 which alsoreceives the signal from transmitter 36 through the conduit 72. Relay 70is supplied with instrument air form a line 74 through a regulator 76and develops from its input signals a composite signal which isindicative of the weight rate of flow of the oxidizing gas passingthrough supply line 20.

This composite output signal is pneumatic in nature and is carried by aconduit 78 to a ratio setting device 80 where the input signal isselectively varied to represent a desired proportion of fuel tooxidizing gas. The ratio setting device 80 may conveniently take theform of a variable orifice or some other arrangement capable ofestablishing an output signal which is a selected fraction of its inputsignal. Suitable proportions of fuel to oxidizing gas have been found tobe on the order of 1 or 2%.

The output of ratio setting device 80 is passed to similar controlequipment associated with each of the tuyeres 24. Specifically, thepneumatic signal from devic 80 is carried by a conduit 82 which dividesinto branch lines 84 and 86, branch line 84 carrying the output ofdevice 80 to a controller 88 associated with one of the tuyeres 24 andbranch line 86 carrying the output signal to a controller, not shown,associated with the other one of the illustrated tuyeres. By controllingthe flow of fluid fuel at each of the tuyeres from a single mastersignal developed by the ratio setting device 80, assurance that therewill be uniform flow of fuel through all of the tuyeres is achieved.

The controller 88 operates a valve 90 which is disposed in the fuel linebetween header 28 and a nozzle 30 as is shown in FIG. 2. Specifically,the valve 90 is connected to a control unit 92 which is spring-loaded todirect the valve 90 normally into a closed position, unit 92 beingfurther arranged to open valve 90 in compliance with a pneumatic signalfrom controller 88. Instrument air is provided to the unit 92 through aline 94, a check and throttling valve 96 being advantageously interposedbetween the unit 92 and the controller 88.

In order to insure proper operation of valve 90, i.e. in order to insurethat the quantity of fluid fuel passing through the valve conforms withthe requirement established at controller 88, means are provided forsensing the flow of the fiuid fuel at a location downstream from thevalve 90. In the embodiment illustrated in FlG. 2, these means includean orifice meter indicated generally at 98 and a differential pressuretransmitter 100. The orifice meter 98 includes a pair of spaced-apartorifice plates 102 and 104 which are connected in a fuel line 106between valve and the nozzle 30. The pressure indications developed bythe orifice plates 102 and 104 are conducted to the transmitter throughsuitable regulating valves such as the valves 108. The transmitter 100,like the transmitter 36, may be of any conventional design andconfiguration, a specific embodiment to be hereinafter described withreference to FIG. 5. The transmitter 100 receives instrument air from aline 110 and converts the pressure indications from orifice plates 102and 104 to a single pneumatic signal indicative of the volumetric flowof fluid fuel passing through the line 106. This output signal fromtransmitter 100 is passed through a conduit 112 to the controller 88 forpurposes of modifying the directed operation of valve 90 in accord withthe flow of fuel actually passing through the valve. Instrument air isadvantageously supplied to the controller 88 through a line 114.Furthermore, a check valve 116 may be interposed in line 106 betweenorifice plate 102 and nozzle 30 if desired.

Similar elements and components are arranged with the other of thetuyeres.

The embodiment of FIGS. 1-3 is particularly arranged to employ fluidfuel of a gaseous nature, such as for example natural gas ormanufactured gas; and it has proved important to arrange the system ofthe invention in such a fashion that situations inherent from the use offuel of this character do not present a safety hazard. The blast furnace12 is intended to be operated at an elevated temperature, and it hasbeen found that fuel gas can decompose at the furnace temperature todeposit carbon in the tuyeres 24. Blockages resulting from carbondeposits are capable of restricting fiow through the tuyeres and ofpermitting fuel gas from the nozzles 30 to backup into the bustle pipe22. If appreciable quantities of the fuel gas collect in the bustlepipe, an explosive mixture can be developed. As will be recognized,blockage of a tuyere 24, as for example might be incurred by thedeposition of carbon from decomposing fuel gas, results in a reducedflow of the oxidizing gas through the tuyere; and this fact can beemployed in determining the blocked condition and compensating for it.

Moreover, the high temperature at which the furnace 12 operates canweaken and eventually destroy the connection between the tuyere and thebody of the furnace, a condition frequently referred to as burning off.Upon the connection of a tuyere with the furnace so failing, the fuelgas being introduced through nozzle 30 is thereby capable of beingreadily discharged into the atmosphere surrounding the furnace due tothe back pressure of the gases within the furnace. The resultantatmosphere about the blast furnace could develop an explosive mixtureand could also present a toxicity problem to those persons working inthe vicinity of the furnace. As will be recognized, the burning off of atuyere permits more rapid flow from the bustle pipe through theremainder of the tuyere; and this increased rate of flow can be sensedand utilized in terminating the fuel flow through the damaged tuyere.

In accordance with the present invention, means are provided for sensingthe flow of oxidizing gas through each of the tuyeres. Specifically, aninverted impact tube 118 is situated in each of the tuyeres intermediatethe nozzle 30 and the bustle pipe 22. By inverting the impact tube, anegative pressure or vacuum signal related to the volumetric fiowthrough the tuyere is developed; and this pressure signal from theimpact tube 118 is directed to a pair of differential pressure switches120 and 122. In order to provide a common, high pressure reference forthe switches 120 and 122, a pressure switch 124 is pneumaticallyconnected to the bustle pipe 22 by means of a conduit 126, the output ofpressure switch 124 being directed to both of the switches 120 and 122as is shown in FIG. 2.

Switch 120 is particularly arranged for the internal contacts thereof tobe closed when an excessive flow of oxidizing gas develops in therelated tuyere 24, i.e., switch 120 is adapted to signal a burned off orsimilarly defective tuyere, this signal being passed by an electricalcenductor 128. On the other hand, switch 122 is arranged for theinternal contacts thereof to close passing an electrical signal when theflow through tuyere 24 falls below a selected value as sensed by impacttube 118, i.e. switch 122 is adapted to sense obstruction of tuyere 24,the output signal from switch 122 being passed by an electricalconductor 13!).

The conductors 128 and 130 are connected to a common conductor 132 whichpasses the signals from switches 120 and 122 to a solenoid operatedvalve 134 of 3-way configuration, valve 134 exhausting the pneumaticsignal from unit 92 to the atmosphere whereby to permit the spring forcestored in the unit 92 to close the valve 90 terminating flow of fuelthrough valve 90 whenever either the switch 120 or the switch 122 passesa signal to the solenoid valve 134. If desired, a flow indicating andrecording device 136 can be connected in pneumatic circuit with thecontroller 88 and the valve 134 so as to provide visual monitoring andpermanent recordation of the operation of valve 90. Instrument air issupplied to the device 136 through a line 138.

In addition, the conductor 132 is connected with a conductor 140 inorder that the signals from switches 120 and 122 can be directed to arelay station 142. The signals from switches 120 and 122 are directedfrom the relay station 142 to circuits, such as the circuits 144 and146, which are connected to annunciators for audibly indicatingrespectively excessive fiow through a tuyere 24 and insuflicient flowtherethrough. A master manual switch 148 is also connected through relaystation 140 for terminating operation of the entire system should theneed arise.

Automatic cessation of operation of the entire system is also desirableunder certain circumstances, as for example upon failure of the fuelsupply, failure of the oxidizing gas supply, or failure of theinstrument air supply. For purposes of determining proper flow of theoxidizing .gas, a pressure switch 150 is pneumatically connected to thesupply line by a conduit 152 whereby to sense the pressure in the line.The internal contacts of pressure switch 150 are advantageously arrangedto complete a circuit passing an electrical signal through the conductor154 to the relay station 142 upon the pressure in supply line 20dropping below a selected value; and turning to FIG. 3, the signal thusdeveloped by pressure switch 150 is passed by the relay station 142 by aconductor 156 to a 4-way solenoid valve indicated generally at 158. Inresponse to the signal thus passed, the valve 158 is caused to shut offall fuel from a main gas supply line 160. Thus, fuel will not bedirected into the tuyeres 24 in the absence of a proper flow ofoxidizing gas.

Similarly, a pressure switch 162 is pneumatically connected to the gasline downstream from valve 158 by a conduit 164, switch 162 beingarranged so that the internal contacts thereof close passing anelectrical signal to relay station 142 through a conductor 166 uponthepressure in the gas line falling below a selected value. This signalfrom switch 162, is, like the signal from switch 150, passed by therelay station 142 to the conductor 156 and thence to the solenoid valve158 for shutting off the flow of fuel when the pressure thereof fallsbelow the selected value.

The relay station 142 may be similarly arranged with appropriate sensorsto detect a failure in the instrument air pressure and to directsolenoid valve 153 to take the fluid fuel supply from the blast furnacewhenever the instrument air supply becomes defective.

When natural gas is employed as the fuel gas for the system of FIGS.1-3, it is ordinarily delivered to the blast furnace area at a linepressure of 250 p.s.i.g. in order that the system may accommodate gasdemands on the order of 400,000 cubic feet per hour. Continuing withreference to FIG. 3, the gas is passed by the solenoid valve 158 at theinitial pressure to a series of gas regulators indicated by the numeral170. These regulators reduce the gas pressure to a useful range of fromto p.s.i.g. If it is desired to silence the noise incurred in reducingthe gas pressure, a sound silencer 172 may be close-coupled with thereducers downstream thereof.

Completing the disclosed embodiment of FIGS. 1-3 is a flow measuringunit indicated generally by the numeral 174. Unit 174 includes a primarymetering device 176 including orifice plate-s 178 and 180. The pressuresignal from these orifice plates is suitable passed to a differentialpressure transmitter 182 through a suitable system of regulating valves,such as the system of regulating valves 184. The transmitter 182 issupplied with instrument air from a line 185, and the pneumatic outputof the transmitter is passed for pressure and temperature variations inthe gas supply. For this latter purpose, a pressure sensor or tap 187and a temperature sensor or well 188 are connected in the gas line 26downstream from the orifice plates 178 and 180. The signals from thesensors 187 and 188 are passed to transducers 100 and 192 respectively,transducers 190 and 192 receiving instrument air from lines 194 and 196in order to convert the signals from the sensors 187 and 188 topneumatic outputs.

The output signals from transducers 190 and 192 are conducted to apneumatic relay 198 from whence a combined signal is passed to the relay186, relay 198 receiving instrument air from a line 200. The pneumaticoutput of relay 186 is passed to a meter body 202, and the determinationof volumetric flow made at the meter body 202 is passed to a flowrecorder 204. The pneumatic signal which indicates gas line pressure andwhich is passed by transducer 190 is also conducted to the recorder 204for purposes of integrating the flow of gas. A pressure recorder 206 maybe advantageously combined with the recorder 204.

If desired, the system described with reference to FIGS. 1-3 can becombined with systems for analyzing the top gas from the furnace and fordetermining the B.t.u. content of these exhaust gases.

The pressure switches employed in the system of the invention arepressure switches of a known and conventional structure, such as forexample the pressure switch which is shown in detail in FIG. 4. There,the switch 120 will be seen to comprise a housing 210 defining a chamber212 and a chamber 214, which chambers are separated by a flexiblediaphragm 216. Because the pressure switch 120 is intended to be apressure difference switch, the chambers 212 and 214 are connectedrespectively to a high pressure source and to a low pressure source asthrough the conduits 218 and 220 respectively. In the system of FIGS.l3, conduit 218 connects the chamber 212 to the pneumatic output ofpressure switch 124 whereas conduit 220 connects chamber 214 to theoutput of impact tube 118.

The housing 210 also encloses a microswitch arrangement 222; and thediaphragm 216 is arranged to operate the microswitch 222 by means of apin 224 in response to the differential pressure existing betweenchambers 212 and 214. Conductors 226, 228 and 230 are employed in makingthe desired electrical connections with the microswitch 222.

As will be recognized, the system of the invention can usefully employpressure switches adapted to be operated from a single pressure sourceas well as pressure switches arranged to develop a pneumatic rather thanan electrical output.

Similarly, the system of the invention is adapted to utilizedifferential pressure transmitters of a common type. Differentialpressure transmitter 100 is selected to be such a unit; and turning toFIG. 5, the differential pressure transmitter 100 will be seen tocomprise a housing 232 which encloses a diaphragm 234, diaphragm 234separating a chamber 236 from a chamber 238. Advantageously, chamber 236is provided with an opening 240 which is adapted to be connected to ahigh pressure source. In similar manner, chamber 238 is provided with anopening 242 which is adapted to be connected to a low pressure source.

A lever 244 is connected to the diaphragm 234 by a plate arrangement 246whereby a differential pressure applied to the diaphragm 234 causes aforce to act on a lever 248 which is pivotally connected to the lever244 and which is swingably mounted about a pivot 250. The action oflever 248 is employed to operate a switch or to control a valveincorporated with the transmitter by suitable means, as by a link 252. Abellows 254 advantageously seals the lever 248 in the vicinity of pivot250.

Construction of the system and operation thereof is believed obviousfrom the foregoing descriptions.

While a particular embodiment of the system of the invention has beenthus far shown, it should be understood, of course, that the inventionis not limited thereto since many modifications may be made. Thereforeand turning to FIG. 6, a modified embodiment of the invention will beseen particularly arranged to employ fuel in the form of fuel oil. Theembodiment of FIG. 6 incorporates a number of elements and componentssimilar in nature to those employed in the embodiment of FIGS. 1-3.Accordingly, like numerals have been used to designate like parts in thetwo embodiments, the sufiix letter a being utilized to distinguish thoseelements and components associated with the embodiment of FIG. 6.

The embodiment of FIG. 6 is singular in a number of respects. First ofall, an oil header 260 is arranged to replace the gas header, a supplyline 262 delivering fuel oil to the header 260. The header 260 surroundsa blast furnace 12a as does a bustle pipe 220; and in addition, the oilheader 260 is provided with a return line 264 in which there isinstalled a back-pressure relief valve 266. A substantially constantpressure in the oil header 260 is thus insured.

A controller 88a receives the fuel rate signal from a ratio settingdevice 80a to control the fuel valve 90a in a manner similar to theelements 88, 80 and 90 described hereinabove. However, in the embodimentof FIG. 6, monitoring of the actual flow of fuel to a given one of thetuyeres 24a is achieved by means of a rotometer 268 which is situatedupstream of valve 90a in an oil line 270 connecting the valve 90a withheader 260. The output signal from rotometer 268 is passed to controller88a in order to insure that the actual flow through the valve 90a is incompliance with the demand established at the ratio setting device 80a.It is important to point out that positioning of the rotometer 268upstream of the valve 90a insures accurate monitoring of the flowthrough the valve since the rotometer thereby operates at substantiallyconstant oil pressure.

A fuel line 272 connects the valve 90a with nozzle 30a; and while nozzle30a is merely arranged to direct a stream of the liquid fuel into theoxidizing gas being introduced into the furnace, it is to be recognizedthat nozzle 30a may be equally well arranged to provide atomization ofthe liquid fuel. A manual shut-off valve 274, a check valve 276 and apurge connection 278 are also advantageously interposed in the fuel line272 between valve 90a and nozzle 30a.

To prevent the liquid fuel from flooding into the bustle pipe 22a upon atuyere 24a becoming plugged, a Pitot tube 280 is installed in eachtuyere 24:: between the nozzle 30a and the bustle pipe 22a. The velocityhead sensed by the Pitot tube 280 is delivered to a differentialpressure switch 282; and when a desired velocity head is achieved in thetuyere due to proper flow of oxidizing gas, the signal from the Pitottube holds the contacts in the switch 282 so as to energize the coil ofsolenoid valve 134a thereby maintaining instrument air on the controlunit 92a. Thus, valve a is held in an operative condition similar to thevalve 90 described hereinabove.

Upon tuyere 24a becoming plugged or obstructed, the signal from thePitot tube 280 decreases whereupon the differential pressure switch 282in response opens its interal contacts to de-energize the coil ofsolenoid valve 134a, evacuating instrument air from the unit 92a andpermitting valve 90:: to close.

The pressure switch 282 is arranged with internal contacts adapted torespond to both excessive and insfiicient oxidizing gas velocities assensed by the Pitot tube 280. Accordingly, in the event that the tuyere24a breaks off or burns off at the furnace 12a, the excessive flow ofoxidizing gas thus incurred is sensed by the Pitot tube; and inresponse, the internal contacts of pressure switch 282 open to releasethe solenoid valve 134a and deactivate the control unit 92a whereby toclose valve 90a.

The specific examples herein shown and described should be considered asillustrative only. Various changes in structure may occur to thoseskilled in the art; and these changes are to be understood as forming apart of this invention insofar as they fall within the spirit and scopeof the appended claims.

The invention is claimed as follows:

1. A control system comprising; a first sensing means disposed insensible contact with a flow of reactable gas which is subject tofluctuations in its physical conditions, said first sensing means beingarranged for developing a first signal indicative of the volumetric rateof flow of said reactable gas; a second sensing means disposed insensible contact with said flow of reactable gas for developing a secondsignal indicative of the fluctuations of at least one of the physicalconditions of said reactable gas; correction means connected to saidfirst and second signal means for developing a third signal indicativeof a corrected volumetric rate of flow of said reactable gas correctedfor fluctuations of at least one of the physical conditions of saidreactable gas; a plurality of nozzles receiving said flow of reactablegas and directing the same into a reaction mass; means directing a flowof fluid fuel to each of said nozzles; a plurality of means forregulating the flow of said fuel to said nozzles, one of said regulatingmeans being operatively associated with each of said nozzles; and meansindividually associated with each of said regulating means for receivingsaid third signal and operating the associated regulating means inaccordance therewith.

2. A control system comprising: means disposed in sensible contact witha flow of reactable gas which is subject to fluctuations in its physicalconditions, said means being arranged for developing a signal indicativeof the volumetric rate of flow of said gas corrected for changes in atleast one physical condition thereof; a plurality of nozzles receivingsaid flow of reactable gas and directing the same into the reactionmass; means directing a flow of fluid fuel to each of said nozzles; aplurality of means for reguating the flow of said fluid fuel to saidnozzles, one of said regulating means being operatively associated witheach of said nozzles; means individually associated with each of saidregulating means for receiving said signal and operating the associatedregulating means in accordance therewith; flow sensing means measuringthe flow of said fluid fuel to the corresponding nozzle and providing asignal indicative thereof; and means for modifying the operation of saidregulating means in compliance with said last mentioned signal so thatsaid flow of fluid fuel corresponds with the requirement established bysaid first mentioned signal.

3. A system for introducing fluid fuel into a blast furnace having aheader and a plurality of tuyeres directing oxidizing gas under pressurefrom said header into the body of said furnace, said system comprising:means supplying fluid fuel to each of said tuyeres at a rateproportional to the weight of oxidizing gas entering said header,including a fuel line; means for sensing the impact pressure of saidoxidizing gas in one of said tuyeres and for developing output signalsindicative thereof; and means responsive to said output signals forterminating the flow of fuel to said one tuyere upon the flowtherethrough falling above or below a selected range of values,including a valve in said fuel line and a first and a seconddiiferential pressure switch receiving said output signal and arrangedindividually to cause closing of said valve when said impact pressure isrespectively above and below the selected range of values.

4. A system according to claim 3 wherein said means for sensing theimpact pressure of said oxidizing gas is disposed in aid one tuyereintermediate said header and a connection with said first mentionedmeans.

5. A system according to claim 3 wherein said means for sensing theimpact pressure of said oxidizing gas includes an inverted impact tube.

6. The method of controlling the introduction of fluid fuel into the airsupply to a blast furnace comprising the steps of causing a flow of airhaving a variable pressure and temperature; measuring the volumetricflow of air at a first point in its path to the blast furnace;introducing fluid fuel into said flow of air at a second pointdownstream from said first point; sensing the pressure and temperatureof said flow of air adjacent said first point; altering said measurevalue of volumetric flow of air in proportion to the sensed changes inpressure and temperature;

10 and regulating the volumetric flow of said fuel in accordance withthe altered value of volumetric flow of air.

7. The method of controlling the introduction of fluid fuel into the airsupply to a blast furnace comprising the steps of: causing a flow of airhaving a variable pressure and temperature; measuring the volumetricflow of air at a first point in its path to the blast furnace;introducing fluid fuel into said flow of air at a plurality of secondpoints downstream from said first point; sensing the pressure andtemperature of said flow of air adjacent said first point; altering themeasured value of volumetric flow of air in proportion to the sensedchanges in pressure and temperature; and individually regulating thevolumetric fiow of said fuel in accordance with the altered value ofvolumetric flow of air.

References Cited by the Examiner UNITED STATES PATENTS 2,072,384 3/1937Schmidt 13791 X 2,388,669 11/1945 Baker 137--88 X 2,879,056 3/ 1959Wagner 266-29 2,938,782 5/1960 Toulmin 266-29 X 3,165,399 1/1965 Kennedy26629 X OTHER REFERENCES Blast Furnace, Coke Oven, and Raw MaterialsProceedings, vol. 20, 1961 (AIME), pp. 595-598.

JOHN F. CAMPBELL, Primary Examiner.

MARCUS U. LYONS, WHITMORE A. WILTZ,

Examiners.

D. L. REISDORF, I. C. HOLMAN, Assistant Examiners.

1. A CONTROL SYSTEM COMPRISING; A FIRST SENSING MEANS DISPOSED INSENSIBLE CONTACT WITH A FLOW OF REACTABLE GAS WHICH IS SUBJECT TOFLUCTUATIONS IN ITS PHYSICAL CONDITIONS, SAID FIRST SENSING MEANS BEINGARRANGED FOR DEVELOPING A FIRST SIGNAL INDICATIVE OF THE VOLUMETRIC RATEOF FLOW OF SAID REACTABLE GAS; A SECOND SENSING MEANS DISPOSED INSENSIBLE CONTACT WITH SAID FLOW OF REACTABLE GAS FOR DEVELOPING SECONDSIGNAL INDICATIVE OF THE FLUCTUATIONS OF AT LEAST ONE OF THE PHYSICALCONDITIONS OF SAID REACTABLE GAS; CORRECTION MEANS CONNECTED TO SAIDFIRST AND SECOND SIGNAL MEANS FOR DEVELOPING A THIRD SIGNAL INDICATIVEOF A CORRECTED VOLUMETRIC RATE OF FLOW OF SAID REACTABLE GAS CORRECTEDFOR FLUCTUATIONS OF AT LEAST ONE OF HE PHYSICAL CONDITIONS OF SAIDREACTABLE GAS; A PLURALITY OF NOZZLES RECEIVING SAID FLOW OF REACTABLEGAS AND DIRECTING THE SAME INTO A REACTION MASS; MEANS DIRECTING A FLOWOF FLUID FUEL TO EACH OF SAID NOZZLES; A PLURALITY OF MEANS FORREGULATING THE FLOW OF SAID FUEL TO SAID NOZZLES, ONE OF SAID REGULATINGMEANS BEING OPERATIVELY ASSOCIATED WITH EACH OF SAID NOZZLES; AND MEANSINDIVIDUALLY ASSOCIATED WITH EACH OF SAID REGULATING MEANS FOR RECEIVINGSAID THIRD SIGNAL AND OPERATING THE ASSOCIATED REGULATING MEANS INACCORDANCE THEREWITH.
 6. THE METHOD OF CONTROLLING THE INTRODUCTION OFFLUID FUEL INTO THE AIR SUPPLY TO A BLAST FURNACE COMPRISING THE STEPSOF: CAUSING A FLOW OF AIR HAVING A VARIABLE PRESSURE AND TEMPERATURE;MEASURING THE VOLUMETRIC FLOW OF AIR AT A FIRST POINT IN ITS PATH TO THEBLAST FURNACE; INTRODUCING FLUID FUEL INTO SAID FLOW OF AIR AT A SECONDPOINT DOWNSTREAM FROM SAID FIRST POINT; SENSING THE PRESSURE ANDTEMPERATURE OF SAID FLOW OF AIR ADJACENT SAID FIRST POINT; ALTERING SAIDMEASURE VALUE OF VOLUMETRIC FLOW OF A AIR IN PROPORTION TO THE SENSEDCHANGES IN PRESSURE AND TEMPERATURE; AND REGULATING THE VOLUMETRIC FLOWOF SAID FUEL IN ACCORDDANCE WITH THE ALTERED VALUE OF VOLUMETRIC FLOW OFAIR.